The position of the subducting Cocos Plate beneath Mexico is unknown from the Trans-Mexican Volcanic Belt (TMVB) northward. Geochemical analysis suggests that there may be a slab tear causing mafic volcanism along the northern edge of the (TMVB). An array of 100 seismometers at 5 km spacing is currently installed in Mexico by the MesoAmerican Seismic Experiment (MASE) in conjunction with the Center for Embedded Networked Sensing (CENS) at UCLA, the Universidad Nacional Autonoma de Mexico (UNAM), and the California Institute of Technology (CIS). The data from this array is used to develop P and S wave tomographies to locate the slab. Beneath the MASE line the Cocos plate dips from the trench to a ~ 50 km depth. It is almost subhorizontal between 110 km to 275 km from the trench at a ~50 km depth. Then it continues to dip at a near constant angle.

Wireless sensor networks using 802.11b long-distance links enable domain scientists to measure physical phenomena in real time and at a scientifically meaningful scale. Although deployments in this setting are increasing, a characterization of the network- throughput is lacking which makes it difficult to predict the performance of sensing applications on these types of networks. We present a study of the MASE seismic data collection network which includes 64 nodes spread across mountains, valleys, rural plains, and urban environments. The network spans 250km with links as long as 43km and has been operating continuously for more than 2 years. The contributions of this paper are three fold: (a) we present a throughput characterization of wireless links for a network in operational use, (b) we suggest settings for the wireless parameters to improve the performance of the network, and (c) we document the uptime of the nodes and the data yield of the network. Our findings are beneficial for the design of future wireless sensor network deployments using 802.11b.

In our networks widely varied settings, we find that while signal-to-noise ratio is not correlated with throughput or distance, throughput is roughly correlated with distance and does not change significantly over time. At the link-layer, enabling the RTS-CTS handshake decreases the throughput while enabling retries improves the throughput. In addition, the default threshold-based rate adaptation algorithm for the transmission bit-rate is suboptimal. We find that the majority of fault cases are due to system issues and not network issues. The data yield over the course of an eight month period was 78%.

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Technological and scientific preparations are occurring for the development of a multi-hop radio-linked seismic array (MHRLSA) of 50 broadband stations (GURALP 3ts) and its first few deployments. A ruggedized data relay device (DRD) is being fabricated using Intel’¡Çs new low power, small form factor stargate motherboard. A DRD will be placed at each node of the array and configured as a local area network (LAN) with station spacing up to 10 km. The objective is to use protocols that have been developed for the world wide web to optimize the acquisition of real time seismic array data...

The Seismic Applications group is working to increase the practical limits of the density of seismic deployments and move to more rapid data gathering in temporary deployments. Temporary deployments in seismology typically consist of stand-alone sites in order to decrease installation time. Data must be collected either periodically from each site or at the end of the experiment and incorporated into a data base for analysis. Permanent seismic installations do transmit data immediately to central data bases through ethernet, point-to-point radio, and modem. We add the ’¡Èreal-time’¡É data collection of permanent installations to temporary networks with multi-hop networking. Off-the-shelf 802.11 wireless radio cards are incorporated with an Intel Stargate computer running Roofnet networking software. In-house software is developed to collect data and route it hop-by-hop through the network to a central data repository. Hop-by-hop data movement allows data to pass effectively through the radio network despite breaks or flaky links within the network.

We will provide TDMA-based state-synchronization service that will provide low latency and high reliability. Our TDMA service will be built on top of the existing MAC found in the radios for Aensbox. We will provide deployment tools, which will enable the deployer to gauge the quality of the deployed network. Our tools will use above mentioned efficient and reliable state-synchronization service and will work without assuming any end-to-end routing service. We will provide system software for Aensbox, which a multi-processor and multi-radio platform. The desired system software must utilize dual processor and radio depending upon the energy consumption of the operation, e.g. a continuous battery monitoring operation can be delegated to a low power processor (MSP), while analysis of a large data-set will be done by high power processor (XScale). Although, comprehensive evaluation of the entire system can be done only at the real scale, it is necessary to gain confidence at early stages of development where real deployment is not possible.

The first long term scientific deployment of the portable broadband seismic array is a part of MASE (Middle America Subduction Experiment) in collaboration with California Institute of Technology and Universidad Nacional Autnoma de Mexico (UNAM). We are mapping the subducted slab beneath Mexico and examining slow earthquakes which have been observed at this subduction zone, volcanic earthquakes and the propagation of seismic waves in Mexico City which was devastated in the 1985 Michoacan earthquake. We will compare our 50 instrument wireless array with the 50 instruments of a stand-alone array that has been installed by Caltech. The transect covered by all stations is 500 km long between Acapulco-Mexico City-Tampico.

The Middle America Subduction Experiment (MASE) is a collaborative project between California Institute of Technology, Universidad Nacional Autonoma de Mexico (UNAM) and UCLA CENS. The project is instrumenting a 500-km transect from Acapulco to Mexico City to Tampico by installing 100 broadband seismometers located every 5 to 20 km. UCLA has installed almost 50 seismometers covering nearly one-half of the line and is using telemetry technology designed by CENS. The entire line will be operating for at least one full year. The seismic data collected by UCLA seismometers is delivered to a RAID array at UCLA in near real time for archiving, processing, and analysis. We are mapping the structure of the Cocos plate subduction zone underneath the Pacific plate along the transect and examine slow earthquakes, volcanic earthquakes and propagation of seismic waves in the heavily populated Mexico City region.

This work describes preliminary results from a 50 station broadband seismic network recently installed from the coast to the high Andes in Peru. UCLA's Center for Embedded Network Sensing (CENS) and Caltech's Tectonic Observatory are collaborating with the IRD (French L'Institut de Recherche pour le Developpement) and the Institute of Geophysics, in Lima Peru in a broadband seismic experiment that will study the transition from steep to shallow slab subduction. The currently installed line has stations located above the steep subduction zone at a spacing of about 6 km. In 2009 we plan to install a line of 50 stations north from this line along the crest of the Andes, crossing the transition from steep to shallow subduction. A further line from the end of that line back to the coast, completing a U shaped array, is in the planning phase. The network is wirelessly linked using multi-hop network software designed by computer scientists in CENS in which data is transmitted from station to station, and collected at Internet drops, from where it is transmitted over the Internet to CENS each night. The instrument installation in Peru is almost finished and we have been receiving data daily from 47 stations (out of total 49) since Jan 2009. Two remain without any network connectivity. The software system provides dynamic link quality based routing, reliable data delivery, and a disruption tolerant shell interface for managing the system from UCLA without the need to travel to Peru. The near real-time data delivery also allows immediate detection of any problems at the sites. We are building a seismic data and GPS quality control toolset that would greatly minimize the station's downtime by alerting the users of any possible problems.